ANATOMY AND PHYLOGENY OF THE CONIFERALES. 153 



In the species under consideration there is a very much greater relative reduction of the 

 upper series of bundles than is the case in /v gigantea. The commissures of transfusion 



tissue, which are so marked, especially in the lower bundles of the cone scales of the 

 hitter species, are much less well developed in the Redwood. The fibrovascular bundles 

 of the fructiferous scales of S. sempervirens show no annual Increments of growth and 



never contain resin ducts. 



The Root of the Skquoias. 



Figure 32, plate 71, illustrates the structure of a small root in S. gigantea. It is 

 obviously pentarchous in its organization and very much resembles a root of Pinus 

 sfrobus or some other Abiet ineous species with large polyarch roots. The protoxylem 

 groups, however, which occupy the apices of the five rays of the primary wood, differ 

 from those of species of Pinus, etc., in not embracing resin ducts. Although the roots of 

 the species under consideration are generally pentarchous, examples are not infrequently 

 found in which there are only four rays of primary wood. This state of affairs also occurs 

 in Pinus strobus. The primary root of all seedlings of 8. gigantea which I have exam- 

 ined is of the tetrarchous type. 1 have never found resin canals present in the secondary 

 wood of this species except as the result of injury. 



The root of S. semjjervirens is so similar to that of 8. gigantea as scarcely to merit a 

 separate description. The symmetry of the root is, however, almost always tetrarchous 

 and the various histological elements are somewhat larger than in the latter species. 



Conclusions. 



In the foregoing paragraphs, attention has been called to the occurrence of resin 

 ducts, under certain definite conditions, in the wood of Sequoia. In 8. (jvjuntea, which in 

 all probability is the more primitive of the two surviving species, resin canals are con- 

 stantly present in the wood of the peduncle, of the axis, and of the scales of the female 

 cone. They also frequently occur in the first annual ring of the more vigorous branches 

 of adult trees. Resin ducts likewise are sometimes found in the leaf traces of the larger 

 leaves of well nourished, mature individuals. Finally, it is possible to bring about the 

 formation of resin canals in tangential rows as the result of injury to the woody cylinder 

 of the root stem and cone of 8. gigantea. The resin ducts occurring in the various situ- 

 ations cited above, form entirely separate systems which do not communicate in any way 

 with each other. In 8. sempervirens, in contrast to the species just referred to, there are 

 no resin canals in the woody tissues either of the reproductive organs, or of young 



